We intend to investigate the molecular mechanisms leading to the formation of maltase in S. cerevisae. We will define the nature of the regulatory system involved in maltase synthesis and the physical properties of the regulatory protein involved in the induction of maltase and maltose permease. We have recently shown that the MAL6 gene is a complex locus consisting of three genes necessary for maltose fermentation: a regulatory gene, the maltase structural gene, and a gene for maltose permease. We have also recently cloned the MAL6 locus. The cloned regulatory gene will be used to identify and isolate the MAL6 regulatory protein. Attempts will then be made to reconstitute the system in vitro by studying the binding of the regulatory protein to the cloned structural gene. These studies of normal maltase synthesis will be complemented by genetic studies of mutants altered in maltase production. We shall isolate, using both classical mutagenesis and in vitro mutagenesis techniques, mutants in all three genes of the MAL6 locus and in their controlling sequences. This combination of biochemical and genetic approaches will allow a complete description of the regulation of maltase synthesis in S. cerevisae.